Who else would have been able to impress Sweeper Monk?

When XF landed his XL18Z on Sweeps, he was impressed. Now the thing was, why would he impressed? XF's internal energy was far far far below his, so it can't be that. Was it because of technique? Not likely, as XL18Z was a simple and straightforward palm technique (this is not to say it isn't good). It could be because XL18Z, as H7G subsequently said while guiding GJ, comprises of simple palm techniques, but the essence lies in how you manipulate your inner energy through it.

Was this the reason why Sweeper Monk was impressed?

Going by this logic, who else would be able to impress Sweeper Monk?

YD? His Yiyang Finger was said to have reached the pinnacle.